// ASM: a very small and fast Java bytecode manipulation framework
// Copyright (c) 2000-2011 INRIA, France Telecom
// All rights reserved.
//
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// modification, are permitted provided that the following conditions
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//    notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
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//    this software without specific prior written permission.
//
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package cn.taketoday.context.asm;

/**
 * A visitor to visit a Java class. The methods of this class must be called in
 * the following order: {@code visit} [ {@code visitSource} ] [
 * {@code visitModule} ][ {@code visitNestHost} ][ {@code
 * visitOuterClass} ] ( {@code visitAnnotation} | {@code visitTypeAnnotation} |
 * {@code
 * visitAttribute} )* ( {@code visitNestMember} | {@code visitInnerClass} |
 * {@code visitField} | {@code visitMethod} )* {@code visitEnd}.
 *
 * @author Eric Bruneton
 */
public abstract class ClassVisitor {

  /**
   * The class visitor to which this visitor must delegate method calls. May be
   * null.
   */
  protected ClassVisitor cv;

  /**
   * Constructs a new {@link ClassVisitor}.
   */
  public ClassVisitor() {
    this(null);
  }

  /**
   * Constructs a new {@link ClassVisitor}.
   *
   * @param classVisitor
   *         the class visitor to which this visitor must delegate method
   *         calls. May be null.
   */
  public ClassVisitor(final ClassVisitor classVisitor) {
    this.cv = classVisitor;
  }

  /**
   * Visits the header of the class.
   *
   * @param version
   *         the class version. The minor version is stored in the 16 most
   *         significant bits, and the major version in the 16 least
   *         significant bits.
   * @param access
   *         the class's access flags (see {@link Opcodes}). This parameter
   *         also indicates if the class is deprecated.
   * @param name
   *         the internal name of the class (see
   *         {@link Type#getInternalName()}).
   * @param signature
   *         the signature of this class. May be {@literal null} if the class
   *         is not a generic one, and does not extend or implement generic
   *         classes or interfaces.
   * @param superName
   *         the internal of name of the super class (see
   *         {@link Type#getInternalName()}). For interfaces, the super class
   *         is {@link Object}. May be {@literal null}, but only for the
   *         {@link Object} class.
   * @param interfaces
   *         the internal names of the class's interfaces (see
   *         {@link Type#getInternalName()}). May be {@literal null}.
   */
  public void visit(final int version, final int access, //
                    final String name, final String signature, final String superName, final String[] interfaces) {

    if (cv != null) {
      cv.visit(version, access, name, signature, superName, interfaces);
    }
  }

  /**
   * Visits the source of the class.
   *
   * @param source
   *         the name of the source file from which the class was compiled. May
   *         be {@literal
   *         null}.
   * @param debug
   *         additional debug information to compute the correspondence between
   *         source and compiled elements of the class. May be {@literal null}.
   */
  public void visitSource(final String source, final String debug) {
    if (cv != null) {
      cv.visitSource(source, debug);
    }
  }

  /**
   * Visit the module corresponding to the class.
   *
   * @param name
   *         the fully qualified name (using dots) of the module.
   * @param access
   *         the module access flags, among {@code ACC_OPEN},
   *         {@code ACC_SYNTHETIC} and {@code
   *         ACC_MANDATED}.
   * @param version
   *         the module version, or {@literal null}.
   *
   * @return a visitor to visit the module values, or {@literal null} if this
   * visitor is not interested in visiting this module.
   */
  public ModuleVisitor visitModule(final String name, final int access, final String version) {
    if (cv != null) {
      return cv.visitModule(name, access, version);
    }
    return null;
  }

  /**
   * Visits the nest host class of the class. A nest is a set of classes of the
   * same package that share access to their private members. One of these
   * classes, called the host, lists the other members of the nest, which in turn
   * should link to the host of their nest. This method must be called only once
   * and only if the visited class is a non-host member of a nest. A class is
   * implicitly its own nest, so it's invalid to call this method with the visited
   * class name as argument.
   *
   * @param nestHost
   *         the internal name of the host class of the nest.
   */
  public void visitNestHost(final String nestHost) {
    if (cv != null) {
      cv.visitNestHost(nestHost);
    }
  }

  /**
   * Visits the enclosing class of the class. This method must be called only if
   * the class has an enclosing class.
   *
   * @param owner
   *         internal name of the enclosing class of the class.
   * @param name
   *         the name of the method that contains the class, or {@literal null}
   *         if the class is not enclosed in a method of its enclosing class.
   * @param descriptor
   *         the descriptor of the method that contains the class, or
   *         {@literal null} if the class is not enclosed in a method of its
   *         enclosing class.
   */
  public void visitOuterClass(final String owner, final String name, final String descriptor) {
    if (cv != null) {
      cv.visitOuterClass(owner, name, descriptor);
    }
  }

  /**
   * Visits an annotation of the class.
   *
   * @param descriptor
   *         the class descriptor of the annotation class.
   * @param visible
   *         {@literal true} if the annotation is visible at runtime.
   *
   * @return a visitor to visit the annotation values, or {@literal null} if this
   * visitor is not interested in visiting this annotation.
   */
  public AnnotationVisitor visitAnnotation(final String descriptor, final boolean visible) {
    if (cv != null) {
      return cv.visitAnnotation(descriptor, visible);
    }
    return null;
  }

  /**
   * Visits an annotation on a type in the class signature.
   *
   * @param typeRef
   *         a reference to the annotated type. The sort of this type reference
   *         must be {@link TypeReference#CLASS_TYPE_PARAMETER},
   *         {@link TypeReference#CLASS_TYPE_PARAMETER_BOUND} or
   *         {@link TypeReference#CLASS_EXTENDS}. See {@link TypeReference}.
   * @param typePath
   *         the path to the annotated type argument, wildcard bound, array
   *         element type, or static inner type within 'typeRef'. May be
   *         {@literal null} if the annotation targets 'typeRef' as a whole.
   * @param descriptor
   *         the class descriptor of the annotation class.
   * @param visible
   *         {@literal true} if the annotation is visible at runtime.
   *
   * @return a visitor to visit the annotation values, or {@literal null} if this
   * visitor is not interested in visiting this annotation.
   */
  public AnnotationVisitor visitTypeAnnotation(final int typeRef, final TypePath typePath, final String descriptor,
                                               final boolean visible) //
  {
    if (cv != null) {
      return cv.visitTypeAnnotation(typeRef, typePath, descriptor, visible);
    }
    return null;
  }

  /**
   * Visits a non standard attribute of the class.
   *
   * @param attribute
   *         an attribute.
   */
  public void visitAttribute(final Attribute attribute) {
    if (cv != null) {
      cv.visitAttribute(attribute);
    }
  }

  /**
   * Visits a member of the nest. A nest is a set of classes of the same package
   * that share access to their private members. One of these classes, called the
   * host, lists the other members of the nest, which in turn should link to the
   * host of their nest. This method must be called only if the visited class is
   * the host of a nest. A nest host is implicitly a member of its own nest, so
   * it's invalid to call this method with the visited class name as argument.
   *
   * @param nestMember
   *         the internal name of a nest member.
   */
  public void visitNestMember(final String nestMember) {
    if (cv != null) {
      cv.visitNestMember(nestMember);
    }
  }

  /**
   * Visits information about an inner class. This inner class is not necessarily
   * a member of the class being visited.
   *
   * @param name
   *         the internal name of an inner class (see
   *         {@link Type#getInternalName()}).
   * @param outerName
   *         the internal name of the class to which the inner class belongs
   *         (see {@link Type#getInternalName()}). May be {@literal null} for
   *         not member classes.
   * @param innerName
   *         the (simple) name of the inner class inside its enclosing class.
   *         May be {@literal null} for anonymous inner classes.
   * @param access
   *         the access flags of the inner class as originally declared in the
   *         enclosing class.
   */
  public void visitInnerClass(final String name, final String outerName, final String innerName, final int access) {
    if (cv != null) {
      cv.visitInnerClass(name, outerName, innerName, access);
    }
  }

  /**
   * Visits a field of the class.
   *
   * @param access
   *         the field's access flags (see {@link Opcodes}). This parameter
   *         also indicates if the field is synthetic and/or deprecated.
   * @param name
   *         the field's name.
   * @param descriptor
   *         the field's descriptor (see {@link Type}).
   * @param signature
   *         the field's signature. May be {@literal null} if the field's type
   *         does not use generic types.
   * @param value
   *         the field's initial value. This parameter, which may be
   *         {@literal null} if the field does not have an initial value, must
   *         be an {@link Integer}, a {@link Float}, a {@link Long}, a
   *         {@link Double} or a {@link String} (for {@code int},
   *         {@code float}, {@code long} or {@code String} fields
   *         respectively). <i>This parameter is only used for static
   *         fields</i>. Its value is ignored for non static fields, which must
   *         be initialized through bytecode instructions in constructors or
   *         methods.
   *
   * @return a visitor to visit field annotations and attributes, or
   * {@literal null} if this class visitor is not interested in visiting
   * these annotations and attributes.
   */
  public FieldVisitor visitField(final int access, final String name, final String descriptor, final String signature,
                                 final Object value) //
  {
    if (cv != null) {
      return cv.visitField(access, name, descriptor, signature, value);
    }
    return null;
  }

  /**
   * Visits a method of the class. This method <i>must</i> return a new
   * {@link MethodVisitor} instance (or {@literal null}) each time it is called,
   * i.e., it should not return a previously returned visitor.
   *
   * @param access
   *         the method's access flags (see {@link Opcodes}). This parameter
   *         also indicates if the method is synthetic and/or deprecated.
   * @param name
   *         the method's name.
   * @param descriptor
   *         the method's descriptor (see {@link Type}).
   * @param signature
   *         the method's signature. May be {@literal null} if the method
   *         parameters, return type and exceptions do not use generic types.
   * @param exceptions
   *         the internal names of the method's exception classes (see
   *         {@link Type#getInternalName()}). May be {@literal null}.
   *
   * @return an object to visit the byte code of the method, or {@literal null} if
   * this class visitor is not interested in visiting the code of this
   * method.
   */
  public MethodVisitor visitMethod(final int access, final String name, final String descriptor,
                                   final String signature, final String[] exceptions) //
  {
    if (cv != null) {
      return cv.visitMethod(access, name, descriptor, signature, exceptions);
    }
    return null;
  }

  /**
   * Visits the end of the class. This method, which is the last one to be called,
   * is used to inform the visitor that all the fields and methods of the class
   * have been visited.
   */
  public void visitEnd() {
    if (cv != null) {
      cv.visitEnd();
    }
  }
}
